A substrate processing system has a substrate carrying-in/out unit that is referred to as a load port or the like. A front opening unified pod (FOUP) configured to contain multiple substrates such as semiconductor wafers, or a substrate transfer container called carrier is carried into the substrate carrying-in/out unit. The substrates in the substrate transfer container are extracted by a first substrate transfer device provided for the substrate processing system and are then moved to an intermediate place for placing the substrate thereon that is referred to as a buffer or the like. After that, the substrates are extracted from the intermediate place by a second substrate transfer device installed in a region where a large number of processing units are arranged. The substrates are subsequently transferred into the processing units. The processing units each execute a predetermined process on the substrates.
As described in JP-2013-165119-A, the substrate transfer devices or substrate transfer robots each have a frame capable of moving in a horizontal direction (Y axis), an ascending and descending body capable of moving in a vertical direction (Z axis) along the frame, a base capable of rotating around a vertically directional axis line (θ axis) with respect to the ascending and descending body, and a plurality of substrate holders (referred to as picks, forks, or the like) capable of being advanced to and retracted from the base in the horizontal direction (X axis). Since orthogonal coordinate system robots of the aforementioned type can detect relative positions between the substrate holders and the substrates with the use of a sensor installed in the base, the robots are further capable of correcting detected positional displacement and placing the substrates on target transfer destinations. These operations improve the reliability of the transfer of the substrates by the substrate transfer devices.
However, in a horizontal articulated robot, if sensors for achieving the aforementioned function are attached to the horizontal articulated robot itself, the movement of an arm might be limited in order to avoid collision of arm with members holding the sensors.